Which is the correct formula for the compound Chromium (II) Nitrate?
a. (Cr)2NO3
b. Cr2NO3
c. CrNO2
d. Cr(NO3)2
The Correct Answer and Explanation is :
The correct formula for Chromium (II) Nitrate is d. Cr(NO₃)₂.
Explanation:
To understand why Cr(NO₃)₂ is the correct formula for Chromium (II) Nitrate, we first need to break down the components of the compound.
- Identifying the Components:
- Chromium (Cr) is a transition metal that can exhibit multiple oxidation states. In this case, “Chromium (II)” indicates that chromium has a +2 oxidation state.
- Nitrate (NO₃) is a polyatomic ion with a -1 charge. Therefore, to balance the charge of the +2 from chromium, we need two nitrate ions.
- Writing the Formula:
- Since we need two nitrate ions to balance the +2 charge from the chromium, we write the formula as Cr(NO₃)₂. Here, the parentheses are essential because they indicate that the entire NO₃ ion is being multiplied by 2.
- Analyzing the Other Options:
- a. (Cr)₂NO₃: This suggests two chromium atoms and one nitrate ion, which does not balance the charges correctly.
- b. Cr2NO₃: This implies two chromium atoms with one nitrate ion, which again does not match the charge balance needed for Chromium (II).
- c. CrNO₂: This formula suggests a different oxidation state of chromium (possibly +1) and the use of nitrite (NO₂) instead of nitrate, which is incorrect for this compound.
Conclusion:
Thus, the correct chemical formula for Chromium (II) Nitrate is Cr(NO₃)₂. This indicates one chromium ion in the +2 oxidation state combined with two nitrate ions, resulting in a neutral compound. Understanding the charge balance and the use of polyatomic ions is crucial in writing the correct chemical formulas for ionic compounds.